Unless otherwise indicated herein, the description in this section is not prior art to the claims in this application and is not admitted to be prior art by inclusion in this section.
Since directions of upper edges of a bundle of documents set at a document feeding unit are not always aligned, the following technique has been proposed. The technique automatically determines set document directions of respective pages based on read original image data. Based on the determination result, the technique performs a rotation process on the original image data on the respective pages as necessary to automatically align upper edges of the original image data upward.
The determination process of set document direction is generally performed based on characters itself, which have directionality, and a layout with page number notation or similar. If the bundle of documents includes a document that includes only a photograph or an illustration or a blank document, the set document direction is failed to be determined or results in erroneous determination. Accordingly, the document that includes only a photograph or an illustration may have a different upper edge from other pages. For example, as illustrated in FIG. 16, if the third page is a document that includes only a photograph or an illustration and therefore the set document direction is failed to be determined or results in erroneous determination, the rotation process possibly rotates the document in any direction. The possibility of rotation in correct direction is around one-quarter.
Therefore, if the set document direction is failed to be determined, there has been proposed a technique that determines the set document direction with reference to a back surface. Alternatively, there has been proposed a technique that determines only a set document direction of a first page, and the technique performs the rotation process same as the rotation process of the first page on original image data on all pages based on the determination result.
However, determining the set document direction with reference to the back surface is effective to a document whose front and back surfaces are mistakenly set or a duplex printed document. However, there is a problem that such technique cannot handle a document where only a photograph or an illustration is printed on one surface.
Assume that the rotation process same as the rotation process of the first page is performed on the original image data on all pages based on the determination result of the first page. If directions of images on some pages differ from images on other pages among the bundle of documents, there is a problem that only these some pages have upper edges different from other pages. For example, as illustrated in FIG. 17, assume that the set document direction on the fourth page has an upper-edge at back and therefore differs from an upper-edge at left, which is the set document direction of the first page. Then, the original image data on the fourth page is rotated right by 90 degree same as the rotation of the first page, thus setting a different upper edge only to the original image data on the fourth page.